island / isolated grids
battery storage / charging stations
Off-Grid Battery-Based Microhydro-Electric Systems
Most small off-grid hydro systems are battery-based. Battery
systems have great flexibility and can be
combined with other energy sources, such as wind generators and
arrays, if the stream is seasonal. Because stream flow is usually
battery charging is as well, and it´s often possible to use a relatively
battery bank. Instantaneous demand (watts) will be limited not by the water potential or turbine, but by the size of the inverter.
The following illustration includes the primary
components of any off-grid battery-based microhydro-electric system..
Off-Grid Batteryless Microhydro-Electric Systems
If the stream has enough potential, one may decide to
go with an AC-direct system. This consists of a turbine generator that
AC output at 120 or 240 volts, which can be sent directly to standard
loads. The system is controlled by diverting energy in excess of load
to dump loads, such as water- or air-heating elements. This technique
total load on the generator constant. A limitation of these systems is
peak or surge loads cannot exceed the output of the generator, which is
determined by the stream´s available head and flow. This type of system
to be large to meet peak electrical loads, so it can often generate
energy for all household needs, including water and space heating.
The following illustration includes the primary components
of any off-grid batteryless microhydro-electric system.
Grid-Tied Batteryless Microhydro-Electric Systems
Systems of this type use a turbine and controls to
produce electricity that can be fed directly into utility lines. These
either AC or DC generators. AC systems will use AC generators to sync
with the grid. An approved interface device is needed to prevent the
from energizing the grid when the grid is out of action and under
systems will use a specific inverter to convert the output of a DC hydro
turbine to grid-synchronous AC. The biggest drawback of batteryless
that when the utility is down, your electricity will be out too. When
fails, these systems are designed to automatically shut down.
The following illustration includes the primary
components of any grid-tied batteryless microhydro-electric system.
[[|]]Microhydro-Electric System Components
AKA: Charge controller, controller, regulator
The function of a
charge controller in a hydro system is equivalent to turning on a load
absorb excess energy. Battery-based microhydro systems require charge
controllers to prevent overcharging the batteries. Controllers generally
excess energy to a secondary (dump) load, such as an air or water heater. Unlike a solar-electric controller, a microhydro system controller does not disconnect the turbine from the batteries. This could create voltages that are higher than some components can withstand, or cause the turbine to overspeed, which could result in dangerous and damaging overvoltages.
AC-direct microhydro systems need controls too. A load-control governor
monitors the voltage or frequency of the system, and keeps the generator
correctly loaded, turning dump-load capacity on and off as the load
changes, or mechanically deflects water away from the runner. Grid-tied
batteryless AC and DC systems also need controls to protect the system
utility grid fails.
AKA: diversion load, shunt load
[[Image:|Dump Load 1]][[Image:|Dump Load 2]]
load is an electrical resistance heater that must be sized to handle the
generating capacity of the microhydro turbine. Dump loads can be air or water heaters, and are activated by the charge controller whenever the batteries or the grid cannot accept the energy being produced, to prevent damage to the system. Excess energy is "shunted" to the dump load when necessary.
AKA: storage battery
reversible chemical reactions, a battery bank provides a way to store
energy when more is being produced than consumed. When demand increases
what is generated, the batteries can be called on to release energy to
your household loads operating.
microhydro system is typically the most gentle of the RE systems on the
batteries, since they do not often remain in a discharged state. The
also be smaller than for a wind or PV system. One or two days of storage
usually sufficient. Deep-cycle lead-acid batteries are typically used in
systems. They are cost effective and do not usually account for a large percentage of the system cost.
battery monitor, amp-hour meter, watt-hour meter
meters measure and display several different aspects of your
microhydro-electric system´s performance and status—tracking how full
battery bank is, how much electricity your turbine is producing or has
produced, and how much electricity is being used. Operating your system
metering is like running your car without any gauges—although possible
it´s always better to know how well the car is operating and how much
in the tank.
[[|]]Main DC Disconnect
AKA: Battery/Inverter disconnect
[[Image:|Main DC Disconnect]]
battery-based systems, a disconnect between the batteries and inverter
required. This disconnect is typically a large, DC-rated breaker mounted
sheet-metal enclosure. It allows the inverter to be disconnected from the batteries for service, and protects the inverter-to-battery wiring against electrical faults.
the DC electricity stored in your battery bank into AC electricity
for powering household appliances. Grid-tied inverters synchronize the system´s output with the utility´s AC electricity, allowing the system to feed hydro-electricity to the utility grid. Battery-based inverters for off-grid or grid-tied systems often include a battery charger, which is capable of charging a battery bank from either the grid or a backup generator if your creek isn´t flowing or your system is down for maintenance.
cases, an inverter and battery bank are used with larger, off-grid
systems to increase power availability. The inverter uses the AC to
batteries, and synchronizes with the hydro-electric AC supply to
when demand is greater than the output of the hydro generator.
[[|]]AC Breaker Panel
AKA: mains panel, breaker box, service entrance
[[Image:|AC Breaker Panel]]
breaker panel, or mains panel, is the point at which all of a home´s
wiring meets with the provider of the electricity, whether that´s the
grid or a
microhydro-electric system. This wall-mounted panel or box is usually
in a utility room, basement, garage, or on the exterior of a building.
contains a number of labeled circuit breakers that route electricity to
rooms throughout a house. These breakers allow electricity to be
for servicing, and also protect the building´s wiring against electrical
the electrical circuits in your home or office, a grid-tied inverter´s
electrical output needs to be routed through an AC circuit breaker. This
breaker is usually mounted inside the building´s mains panel. It enables
inverter to be disconnected from either the grid or from electrical loads if servicing is necessary. The breaker also safeguards the circuit´s electrical wiring.
meter, utility meter
homes with grid-tied microhydro-electric systems will have AC
coming from and going to the utility grid. A multichannel KWH meter
of how much grid electricity you´re using and how much your RE system is
producing. The utility company often provides intertie-capable meters at
A turbine converts the energy in
falling water into shaft power. There are various types of turbine which
categorised in one of several ways. The choice of turbine will depend mainly on the pressure head available and the design flow for the proposed hydropower installation. As shown in table 2 below, turbines are broadly divided into three groups; high, medium and low head, and into two categories: impulse and reaction.
The difference between impulse and
reaction can be explained simply by stating that the impulse
convert the kinetic energy of a jet of water in air into movement by
turbine buckets or blades - there is no pressure reduction as the water
pressure is atmospheric on both sides of the impeller. The blades of a reaction
turbine, on the other hand, are totally immersed in the flow of water,
angular as well as linear momentum of the water is converted into shaft
the pressure of water leaving the runner is reduced to atmospheric or
The load factor is the amount of
power used divided by the amount of power that is available if the
to be used continuously. Unlike technologies relying on costly fuel
the 'fuel' for hydropower generation is free and therefore the plant
more cost effective if run for a high percentage of the time. If the
only used for domestic lighting in the evenings then the plant factor
very low. If the turbine provides power for rural industry during the
meets domestic demand during the evening, and maybe pumps water for
in the evening, then the plant factor will be high.
It is very important to ensure a
high plant factor if the scheme is to be cost effective and this should
taken into account during the planning stage. Many schemes use a 'dump'
(in conjunction with an electronic load controller - see below), which
effectively a low priority energy demand that can accept surplus energy
excess is produced e.g. water heating, storage heaters or storage
Load control governors
Water turbines, like petrol or
diesel engines, will vary in speed as load is applied or relieved.
such a great problem with machinery which uses direct shaft power, this
variation will seriously affect both frequency and voltage output from a
generator. Traditionally, complex hydraulic or mechanical speed
altered flow as the load varied, but more recently an electronic load
controller (ELC) has been developed which has increased the simplicity
reliability of modern micro-hydro sets. The ELC prevents speed
continuously adding or subtracting an artificial load, so that in
turbine is working permanently under full load. A further benefit is
ELC has no moving parts, is very reliable and virtually maintenance
advent of electronic load control has allowed the introduction of simple
efficient, multi-jet turbines, no longer burdened by expensive hydraulic governors.
Load- or Flow- controller ensure that the power output does not exceed the power demand (e.g. 230V, 50 Hz).
If flow of water in a MHP-station is constant the energy output of a turbine/generator is constant as well. Power demand is usually fluctuating over the time (e.g. day/night). If supply is higher than demand, excess energy must be diverted, dumped. alternatively the water flow can be reduced which results in less power output.
In case of more power demand than supply the controller cuts of the of demand line.
Load controller are placed between generator output and the consumer line.
Electronic circuit, which keeps output power constant in Frequency- and Voltage- parameters.
Fluctuating energy demand requires a mechanism which either regulates the water input into the turbine (= flow control) or by diverting excess energy from the consumer connection (= ballast load).
usually electrical heaters in water or air. If energy demand is temporarily low the excess energy is converted into heat.
regulates the amount of water into the turbine in order to match power output and power demand.
Nowadays flow control is done mostly via electronics (which steer a valve)